A long term evolution (LTE) system is an important 3rd generation partnership project. FIG. 1 shows a frame structure of a frequency division duplex (FDD) mode in an LTE system. As shown in FIG. 1, one 10 ms radio frame comprises twenty slots which are 0.5 ms long each and numbered from 0 to 19 respectively. Slot 2i and slot (2i+1) compose subframe i which is 1 ms long. When the LTE system adopts a subframe with a normal cyclic prefix, one slot contains 7 uplink/downlink signals; and when the LTE system adopts a subframe with an extended cyclic prefix, one slot contains 6 uplink/downlink signals. A resource element (RE) is a subcarrier in an orthogonal frequency division multiplexing (OFDM) symbol. FIG. 2 is a schematic diagram showing physical resource blocks in an LTE system of bandwidth 5 MHz based on relevant technologies. As shown in FIG. 2, when the LTE system adopts a subframe with a normal cyclic prefix, one downlink resource block (RB) comprises 12 sequential subcarriers and 7 sequential OFDM symbols; when the LTE system adopts a subframe with an extended cyclic prefix, one RB comprises 12 sequential subcarriers and 6 sequential OFDM symbols, which is 180 kHz in frequency domain and is the duration of one normal slot in time domain. Resource allocation is performed with a resource block as a basic unit.
The LTE system supports applications of 4-antenna multiple-input multiple-out-put (MIMO) system. The corresponding antenna ports #0, #1, #2 and #3 adopt full-bandwidth cell-specific reference signals (CRSs). When the cyclic prefix of a subframe is a normal cyclic prefix, the position of CRSs in the physical resource blocks is shown in FIG. 3; when the cyclic prefix of a subframe is an extended cyclic prefix, the position of CRSs in the physical resource blocks is shown in FIG. 4.
A base station needs to measure the position of a user equipment (UE) in a cell to configure and schedule the UE effectively. At present, the CRS is used to measure the UE, but due to the semi-static configuration of the power of CRSs, its UE positioning performance is limited. An existing solution for the above-mentioned problem is to implement positioning by sending PRSs so as to ensure the positioning precision of the UE. Period of sending PRS is 160 ms, 320 ms, 640 ms or 1280 ms. The number of successive subframes sending PRSs is 1, 2, 4 or 6. The time-frequency position of PRSs in the physical resource blocks is shown in FIG. 5, wherein the left figure shows the time-frequency position of PRSs when a physical broadcast channel adopts single-antenna and double-antenna ports for transmission, and the right figure shows the time-frequency position of PRSs when a physical broadcast channel adopts four-antenna ports for transmission.
A physical downlink control channel (PDCCH) can be transmitted over the first n OFDM symbols in one subframe. For a non-MBSFN (multimedia broadcast/multicast service single frequency network, MBSFN for short) subframe, when the downlink bandwidth is less than or equal to 10 resource blocks, n is 2, 3 or 4. Therefore, when the physical downlink control channel is transmitted over the first four OFDM symbols in the subframe, the data carried by the physical downlink control channel will be in conflict with the PRS over the fourth OFDM symbol, so that a solution is required to avoid such problem so as to ensure the overall performance of the system.